This invention relates to a contact lens formed from a polymer hydrogel made by photopolymerizing a hydroxyalkyl acrylate or methacrylate in the absence of a cross-linking agent.
Hydrophilic plastics for the production of contact lenses have recently gained more and more in interest. Contact lenses of the aforementioned materials are soft and gelatinous, adjust extremely well to the eye and, are therefore more pleasant to wear than lenses made of the conventional, relatively inflexible and unpliable plastics.
It is known to use copolymers of monomeric hydroxyalkyl acrylates or -methacrylates and di- or mono-olefin glycol diacrylates or -methacylates for the production of contact lenses. The monomers are made to polymerize by free-radical forming catalysts at elevated temperature like, for instance, peroxides.
U.S. Pat. No. 3,220,960 to Wichterle et al describes cross-linked hydrophilic polymers that are prepared from esters of acrylic acid and methacrylic acid with alcohols carrying hydrophilic groups. Hydrophilic, plastic contact lenses on the basis of, for instance, hydroxypropyl methacrylate, lauryl methacrylate and polyethyleneglycol methacrylate are the subject matter of U.S. Pat. No. 3,503,946 to Seidermann.
As is known, the water absorptivity of these hydrophilic copolymers depends to a high degree upon the degree of cross-linking, i.e. the desirable high water absorption can be attained only with copolymers with a low degree of cross-linking. However, a disadvantage is that the mechanical and optical properties of such copolymers do not always optimally meet the specifications set forth for contact lenses.
It was therefore necessary to develop a hydrophilic material for the production of contact lenses, which can be prepared in an economical and simple manner, guarantees high water absorption as a result of minimum cross-linking, is gelatinous in the hydrated state, and exhibits mechanical properties which meet the highest standards.